ENFILE

ENFILE is an errno value used by POSIX-compliant kernels to indicate that the system-wide limit on the total number of open files has been reached. It is reported by various system calls that need to allocate a new file descriptor, such as open, accept, or dup, when the global file descriptor table is full and the kernel cannot allocate more descriptors.

In most Unix-like systems, ENFILE stands for "file table overflow." It is defined in errno.h as part of the standard set of error codes. It is distinct from EMFILE, which means that the calling process has exhausted its own per-process limit on open files, even though there may be available descriptors elsewhere in the system.

Impact and handling: When ENFILE is returned, the application should release unused file descriptors and other resources and may retry the operation later if appropriate. If ENFILE persists under normal load, system administrators and developers often address it by adjusting limits. Per-process limits are controlled by RLIMIT_NOFILE (commonly managed with ulimit -n or via limits.conf); system-wide limits are governed by fs.file-max (or relevant kernel parameters via sysctl or systemd configurations). Increasing these values should be done with consideration of overall system capacity and workload, and may require coordinating changes across startup scripts, service units, and resource accounting tools.

Notes: ENFILE is one of the standard POSIX error codes and is part of the broader set of resource exhaustion signals in Unix-like operating systems. Its practical meaning is an indication of a system-wide shortage of file descriptors rather than a shortage within a single process.